Hi I'm a newbe. I just bought an 8" Mak-cass from ebay, the guy I bought it from seems to think its some sort of prototype. The funny thing about this scope is that both Primary, and secondary mirrors are coated on the back side. The Primary mirror is concave on the face side and convex on the back side.The corrector plate is concave on the mirror side and flat the other side. Does anyone know what type of scope this is?

Well, a pic would certainly help. The coatings being on the back side or the primary doesn't make sense to me. Also, a Maksutov has a meniscus, not a corrector. What you are describing sounds much different than a regular Mak. Is the primary perforated, or it there a tertiary mirror as well?

I just reread your post. I think you may have your definitions of primary and secondary reversed. If I'm correct in my guess, the clear glass at the front of the scope with a convex/concave matching curve with a small mirrored spot in the center is actually the meniscus and secondary mirror. The mirror at the back with concave mirrored face and flat back is the primary, which is much larger in size than the secondary spot at the front. IF my guess is correct, you do indeed have a Mak-Cass, but identification of brand is only possible with some good pics.

I was considering bidding on this scope myself- congrats (assuming it works)! I wonder whether this has Mangin mirrors (not just mirrored on the back but the glass is deliberately designed to act as a lens). If images aren't radically distorted then you may have a very interesting project scope!

Yeah, its a Schmidt, not a Mak. The collimatable secondary gives it away. Its possible the primary being coated on the back is merely to protect the coating from physical damage. Not a bad practive, except it is another optical surface for the light to pass through (twice, actually). Questar did something similar with the early 3.5"ers, but for a different reason. They put the secondary spot on the front of the meniscus instead of the back like they currently do to avoid patent infringement of Dmitri Maksutov's design. I think the patent ran out in 1961, and they started putting the secondary on the back.

I'd say this might be just a regular ATMed scope, not necessarily a 'prototype' from a company. The open frame certainly aids in cooldown time. With no baffle tube, there might be some glare issues on bright objects.